KR20240074768A - Self-viscous fluids and mechanical devices - Google Patents

Abstract

A self-viscous fluid and mechanical device that achieve both improvement in drag upon excitation and improvement in rubber resistance properties are provided. A magnetic viscous fluid containing magnetic particles and a base oil, wherein the base oil contains an ester base oil and a non-polar base oil, and the base oil has a non-polar index in the range of 10 to 45.

Description

Self-viscous fluids and mechanical devices

The present invention relates to self-viscous fluids and mechanical devices. In particular, it relates to a self-viscous fluid used to control the frictional force acting between objects in a mechanical device and a mechanical device using the self-viscous fluid. Examples of mechanical devices include brakes, clutches, vibration isolation devices, and dampers of vibration isolation devices.

Magneto Rheological (MR) fluid is a fluid in which magnetic particles, which are magnetizable metal particles, are dispersed in a dispersion medium. A magnetic viscous fluid has magnetic particles floating randomly in a dispersion medium when there is no action of a magnetic field, and functions as a fluid. On the other hand, when a magnetic field is applied, the internal stress of the magnetic viscous fluid increases as magnetic particles form a large number of clusters and thicken.

The self-viscous fluid functions like a rigid body due to the increase in internal stress described above, and exhibits drag against shear flow and pressure flow. Because it has these characteristics, self-viscous fluids are used to control the frictional force acting between objects in various mechanical devices such as brakes, clutches, vibration isolators, and dampers of vibration dampers.

For this reason, it is preferable that the drag force (hereinafter also referred to as “drag force during excitation”) against the shear flow or pressure flow when a magnetic field is applied to the magnetic viscous fluid (at the time of excitation) is larger. Additionally, the drag force during excitation is evaluated by measuring torque value, viscosity, or shear stress. In this specification, the drag force at the time of excitation is evaluated by measuring the viscosity at the time of excitation.

Self-viscous fluids have various characteristics including the drag force upon excitation described above. In recent years, technology has been developed to improve various properties of a self-viscous fluid by preparing a dispersion medium for the self-viscous fluid. As such a technology, Patent Document 1 discloses a self-viscous fluid composition containing monoester, magnetic particles, a dispersant, and a rheology control agent. And according to this configuration, it is described that it is possible to provide a magnetic viscous fluid composition with low viscosity when the magnetic field is turned off, suppressed evaporation amount, and excellent fluidity at low temperatures.

Additionally, Patent Document 2 discloses a magnetic viscous fluid in which the specific gravity and kinematic viscosity of the dispersion medium are controlled within a predetermined range, and the average primary particle diameter, density, and mass ratio of the magnetic particles are controlled to be within a predetermined range. And according to this configuration, it is described that it is possible to provide a magnetic viscous fluid that can significantly suppress sedimentation of magnetic particles without changing the kinematic viscosity of the dispersion medium.

Japanese Patent Publication No. 2017-92119 Japanese Patent Publication No. 2021-163969

Rubber is used as a sealing material such as O-rings, oil seals, and packing in various mechanical devices such as brakes, clutches, vibration isolation devices, and dampers of vibration isolation devices, etc., in which self-viscous fluids are used. At this time, the rubber is in contact with the self-viscous fluid, but the rubber may be deteriorated from the contact portion due to the dispersion medium contained in the self-viscous fluid. When the rubber used in sealing materials such as O-rings, oil seals, and packing deteriorates, it leads to failure of mechanical devices.

For this reason, self-viscous fluids are required not only to improve drag upon excitation but also to have properties that suppress deterioration of rubber (hereinafter also referred to as rubber-resistant properties). However, conventionally, there has been no technology that achieves both the improvement of drag during excitation and the improvement of rubber resistance characteristics.

The present invention was made in consideration of the above points, and its purpose is to provide a self-viscous fluid and a mechanical device that achieve both improvement in drag during excitation and improvement in rubber resistance properties.

In order to solve the above problems, the present invention is specified as follows (1) to (5).

(1) It is a magnetic viscous fluid containing magnetic particles and base oil,

The base oil includes an ester base oil and a non-polar base oil,

A self-viscous fluid, wherein the base oil has a non-polar index in the range of 10 to 45.

(2) The self-viscous fluid according to (1), wherein the ester base oil is at least one selected from hindered esters and dibasic acid esters.

(3) The magnetic viscous fluid according to (1) or (2) above, further comprising alkylbenzene having an alkyl group having 10 to 24 carbon atoms, and/or alkylnaphthalene having an alkyl group having 10 to 24 carbon atoms.

(4) The self-viscous fluid according to any one of (1) to (3) above, further comprising an inorganic cation exchanger having a siloxane bond and a silicone oil.

(5) A mechanical device using the self-viscous fluid according to any of (1) to (4) above.

According to embodiments of the present invention, it is possible to provide a self-viscous fluid and a mechanical device that both improve drag during excitation and improve rubber resistance properties.

Figure 1 is a graph showing the relationship between the nonpolar index in Tables 1 and 2 and the hardness change rate of NBR in Examples 1 to 4, 7 to 14, and Comparative Examples 1 to 3.

Hereinafter, embodiments of the self-viscous fluid and the mechanical device of the present invention will be described, but the present invention is not to be construed as limited thereto, and, based on the knowledge of those skilled in the art, without departing from the scope of the present invention, various Changes, modifications, and improvements can be added.

In addition, in this specification, "to" indicating a numerical range indicates a range including the numerical values respectively described as the upper and lower limits. In addition, when only the upper limit value is described in units in a numerical range, it means that the lower limit value is also in the same units as the upper limit value.

In the numerical range described stepwise in this specification, the upper limit or lower limit value described in one numerical range may be replaced with the upper limit or lower limit value of another numerical range described stepwise.

In addition, in the numerical range described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced with the value shown in the examples.

In this specification, the content rate or content of each component in the composition refers to the total content rate or content of the multiple types of materials present in the composition, unless specifically stated, when multiple types of substances corresponding to each component exist in the composition. means.

(self-viscous fluid)

The magnetic viscous fluid according to the present embodiment is a colloidal fluid containing magnetic particles and a base oil, and the magnetic particles are dispersed in the base oil. The base oil contains an ester base oil and a non-polar base oil. The magnetic particles in the magnetic viscous fluid are floating in the base oil before excitation, and when a magnetic field is applied (excitation), they cluster along the magnetic field. Base oil serves as resistance when clustering. Ester base oil is a synthetic oil and has a more constant molecular structure than mineral oil, so when a magnetic field is applied, the physical resistance between the magnetic particles and the ester base oil is reduced. As a result, the ideal cluster is manipulated and the magnetic properties are increased. However, for the sedimentation stability of magnetic particles, the ester base oil needs to be polar, but most of the polar ester base oils tend to cause the rubber to swell. In contrast, in the magnetic viscous fluid according to the present embodiment, magnetic particles are dispersed in a base oil, and the base oil contains an ester base oil and a non-polar base oil that has the property of shrinking rubber, so the drag force during excitation is improved. and improvement of rubber resistance properties.

The base oil contained in the self-viscous fluid according to the present embodiment includes an ester base oil and a non-polar base oil. Ester base oils have the property of swelling rubber, and non-polar base oils have the property of shrinking rubber. By mixing ester base oil and non-polar base oil having these conflicting properties, the non-polar index consisting of ester base oil and non-polar base oil contained in the self-viscous fluid can be adjusted to a predetermined range, thereby making it possible to adjust the rubber in contact with the self-viscous fluid. Deterioration can be well suppressed.

In addition, the nonpolar index is calculated according to the following formula (A).

Nonpolar index = {(number of carbon atoms × molecular weight) / (number of ester groups × 100)} × {(content of ester base oil) / (content of ester base oil + content of nonpolar base oil)} (A)

(In the above formula (A), the “number of carbon atoms” represents the number of carbon atoms constituting the ester base oil, the “molecular weight” represents the molecular weight of the ester base oil, and the “number of ester groups” represents the number of carbon atoms constituting the ester base oil. indicates the number of ester groups it has)

Here, in the present invention, “deterioration of rubber” refers to the fact that the absolute value of the rate of change in hardness of rubber increases by more than 5% due to contact with a self-viscous fluid for a predetermined period of time. In the magnetic viscous fluid according to the present embodiment, the nonpolar index is in the range of 10 to 45, preferably in the range of 15 to 40, and more preferably in the range of 20 to 40. By setting the non-polar index to 45 or less, deterioration of the rubber can be suppressed, and by setting the non-polar index to 10 or more, the effect of suppressing the sedimentation of magnetic particles can be improved and the drag force during excitation can be improved. In addition, the method for calculating the hardness change rate of rubber will be described later.

In addition, the rubber that can suppress deterioration in the present invention is not particularly limited, but includes acrylonitrile butadiene rubber (hereinafter also referred to as “NBR”), styrene butadiene rubber (SBR), chloroprene rubber (CR), and silicone rubber. , urethane rubber, etc. Among these, NBR is a rubber that is particularly suitably used as a sealing material such as O-rings, oil seals, and packings in various mechanical devices such as brakes, clutches, vibration isolators, and dampers of vibration dampers, and is the magnetic material according to the present invention. The anti-rubber properties of viscous fluids are particularly well demonstrated.

Hereinafter, each component contained in the magnetic viscous fluid according to the present embodiment will be described.

1. Magnetic particles

The magnetic particles contained in the magnetic viscous fluid according to the present embodiment can be selected according to the desired magnetic permeability. For example, ferromagnetic oxides such as magnetite, carbonyl iron, γ iron oxide, manganese ferrite, cobalt ferrite, or composite ferrite of these with zinc and nickel, or barium ferrite; Ferromagnetic metals such as iron, cobalt, and rare earths; metal nitride; Various alloys such as Sendust (registered trademark), Permalloy (registered trademark), and Supermalloy (registered trademark) can be mentioned. Among these, carbonyl iron is preferable because it is a soft magnetic material with small coercive force and high magnetic permeability. Carbonyl iron is a high-purity metal particle produced by thermal decomposition of pentacarbonyl iron (Fe(CO) ₅ ).

In addition, magnetic particles may be used individually or in combination of two or more types.

In the magnetic viscous fluid according to the present embodiment, when a magnetic field is applied from the outside, the dispersed magnetic particles are oriented in the direction of the magnetic field to form chain-like clusters, which thickens and changes the flow characteristics and yield stress. The average particle diameter of the magnetic particles is determined to exhibit this behavior. Specifically, it is preferably in the range of 0.1 to 100 ㎛, more preferably in the range of 1 to 80 ㎛, even more preferably in the range of 5 to 60 ㎛, even more preferably in the range of 10 to 50 ㎛. It is preferable, and it is most preferable that it is in the range of 10 to 40㎛. The shape of the magnetic particles is preferably spherical or nearly spherical because it facilitates dispersion.

In addition, the average particle diameter of the magnetic particles is the average primary particle diameter measured with a laser diffraction/scattering type particle size distribution measuring device.

The content of magnetic particles is preferably in the range of 30 to 90 mass% with respect to the total amount of magnetic viscous fluid according to the present embodiment. By setting the content of magnetic particles in the range of 30 to 90% by mass with respect to the total amount of the magnetic viscous fluid according to the present embodiment, the necessary drag force is obtained when a magnetic field is applied, and the dispersibility of the magnetic particles can be maintained, so that the fluid It also functions as The content of the magnetic particles is more preferably in the range of 40 to 85 mass%, still more preferably in the range of 45 to 80 mass%, and most preferably in the range of 50 to 75 mass%.

2. Base oil

The base oil contained in the self-viscous fluid according to the present embodiment includes an ester base oil, a non-polar base oil, and specific alkylbenzene and alkylnaphthalene added as desired. Ester base oils, non-polar base oils, and specific alkylbenzenes and alkylnaphthalenes will be described in detail below.

2-1. Ester base oil

The ester base oil contained in the self-viscous fluid according to the present embodiment is a polar base oil, and the ester base oil is an ester group-containing compound having an ester group (-C(=O)-O-). Examples of ester base oils include monoesters, polyol esters, dibasic acid esters (diesters), and polyoxyalkylene glycol esters. These ester base oils may be used individually by 1 type, or may be used in combination of 2 or more types.

Among these, the monoester is preferably a monoester having 12 to 30 carbon atoms, and examples include 2-ethylhexyl laurate, 2-ethylhexyl palmitate, and n-butyl stearate. Polyol ester refers to the ester of a polyhydric alcohol (polyol) and a linear or branched saturated or unsaturated fatty acid. Examples of polyol ester include hindered ester.

2-1-1. Hindered ester

As an ester base oil contained in the self-viscous fluid according to the present embodiment, hindered ester will be described in detail as an example. Hindered ester is an ester of a hindered polyol having one or more quaternary carbons in the molecule and having 1 to 4 methylol groups bonded to at least one of the quaternary carbons and an aliphatic monocarboxylic acid.

As hindered polyols, for example trimethylolpropane (TMP), pentaerythritol (PE), dipentaerythritol (DPE), neopentyl glycol (NPG), 2-methyl-2-propyl-1,3-propane. Diol (MPPD), etc. can be mentioned.

Among these hindered polyols, trimethylolpropane, pentaerythritol, and dipentaerythritol are preferable because the flash point of the hindered ester obtained is higher, and trimethylolpropane is more preferable because the pour point of the hindered ester obtained is lowered. .

As the aliphatic monocarboxylic acid, aliphatic monocarboxylic acid having 5 to 15 carbon atoms is preferable. The acyl group of this monocarboxylic acid may be either linear or branched. As aliphatic monocarboxylic acids, for example, valeric acid, caproic acid, caprylic acid, enanthic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, myristic acid, undecylenic acid, rinderic acid, Examples include citric acid, piceteric acid, myristoleic acid, sorbic acid, and sabic acid. At the time of esterification, these aliphatic monocarboxylic acids may be used individually or in combination of two or more types. It is more preferable that the carbon number of the aliphatic monocarboxylic acid is in the range of 5 to 12. It is more preferable that the carbon number of the aliphatic monocarboxylic acid is 5 or more because the flash point of the resulting hindered ester increases. It is more preferable that the carbon number of the aliphatic monocarboxylic acid is 15 or less because the solubility parameter of the resulting hindered ester can be improved. The carbon number of the aliphatic monocarboxylic acid is more preferably in the range of 6 to 10, and most preferably in the range of 7 to 9.

In addition, the carbon number of the fatty acid above includes the carbon atom of the carboxyl group (-COOH) of the fatty acid.

2-1-2. dibasic acid ester

As an ester base oil contained in the self-viscous fluid according to the present embodiment, dibasic acid ester will be described in detail as an example.

Examples of dibasic acid esters include esters of dicarboxylic acids having 2 to 10 carbon atoms and alcohols having 1 to 10 carbon atoms.

Dicarboxylic acids having 2 to 10 carbon atoms, such as oxalic acid, malonic acid, succinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid. and aliphatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid.

Examples of alcohols having 1 to 10 carbon atoms include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, hexanol, octanol, 2-ethylhexanol, isononyl alcohol, decyl alcohol, and isodecyl alcohol. . Among the above dibasic acid esters, diisobutyl adipate, di(2-ethylhexyl) adipate (DOA), diisodecyl adipate (DIDA), diisononyl adipate (DINA), and bis azelaate (2 Dibasic acid esters, which are esters of a dicarboxylic acid with 6 to 10 carbon atoms and an alcohol with 4 to 10 carbon atoms, such as -ethylhexyl) (DOZ) and di(2-ethylhexyl) (DOS), are preferred. . These dicarboxylic acids and alcohols may be used individually or in combination of two or more types during esterification.

Additionally, unless otherwise specified, in the present invention, the carbon number of the aliphatic dicarboxylic acid also includes the carbon atom of the carboxyl group (-COOH) of the aliphatic dicarboxylic acid. Dibasic acid ester may be used individually by 1 type, or may use 2 or more types together.

The ester base oil contained in the self-viscous fluid according to the present embodiment preferably has a kinematic viscosity at 40°C of 50.0 mm2/s or less, more preferably in the range of 10.0 to 50.0 mm2/s, and 10.0 to 40.0 mm2. It is most desirable to be in the range of /s. It is more preferable that the kinematic viscosity of the ester base oil at 40°C is 50.0 mm2/s or less because it becomes easier to disperse the magnetic particles.

In addition, kinematic viscosity is kinematic viscosity measured based on JIS K2283:2000 (kinematic viscosity test method).

The ester base oil contained in the self-viscous fluid according to the present embodiment preferably has a flash point of 200°C or higher, and more preferably 250°C or higher.

If the flash point of the base oil is 200°C or higher, the classification of the base oil composition under the Fire Protection Act changes from 3rd petroleum class to 4th petroleum class, so it is more preferable because the handling amount (designated quantity) of hazardous substances can be increased. In addition, the flash point is the flash point measured based on JIS K2265-4:2007 (Cleveland Opening (COC) method).

The ester base oil contained in the self-viscous fluid according to the present embodiment preferably has a pour point of -10°C or lower, more preferably -20°C or lower, particularly preferably -30°C or lower, and most preferably -50°C or lower. desirable. A pour point of -10°C or lower is more preferable because low-temperature fluidity is excellent. In addition, the pour point is the pour point measured based on JIS K2269:1987.

The solubility parameter of the ester base oil is preferably in the range of 8.5 to 12.0 (cal/cm3) ^1/2 , more preferably in the range of 8.8 to 11.0 (cal/cm3) ^1/2 , and 9.0 to 10.0 (cal/cm3). ㎤) is most preferably in the range of ^1/2 . It is more preferable to set the solubility parameter to 8.5 (cal/cm3) ^1/2 or more because it makes it possible to make the ester base oil and the silicone oil described later incompatible. It is more preferable to set the solubility parameter to 12.0 (cal/cm3) ^1/2 or less because the heat resistance of the ester base oil can be improved.

In addition, the solubility parameter (SP value) can be calculated according to the method proposed by Fedors et al., "see Polymer Engineering and Science, 14, 147-154 (1974)." That is, it can be calculated based on the following equation (B).

SP value δ=(Σ△e/Σ△v) ^1/2 ... (B)

(In the above formula (B), Δe is the evaporation energy of each atom or atomic group at 25°C, and Δv is the molar volume of each atom or atomic group at the same temperature.)

2-2. non-polar base oil

The non-polar base oil contained in the self-viscous fluid according to the present embodiment is a non-polar emulsion consisting only of carbon and hydrogen, and examples include mineral oils such as paraffinic mineral oil and naphthenic mineral oil, polyα-olefin (PAO), α-olefin, Synthetic naphthene oil, polybutene oil, etc. can be mentioned. Among these, polyα-olefin is preferred because it has excellent heat resistance and a high viscosity index. These nonpolar base oils may be used individually or in combination of two or more types.

Among these, preferred naphthenic mineral oils include compounds having a ring selected from a cyclohexane ring, a bicycloheptane ring, and a bicyclooctane ring.

Poly alpha olefin is a poly alpha olefin or a hydride thereof obtained by polymerizing at least one type of alpha olefin in a range of polymerization degrees of 2 to 10.

The polyα-olefin may be a homopolymer of α-olefin, a copolymer of two or more types of α-olefin, or a hydride thereof.

The α-olefin as a raw material may be straight chain or may have branches, but is preferably straight chain. The number of carbon atoms of the α-olefin is not particularly limited, but is preferably 8 to 12, and more preferably 10. Examples of straight-chain α-olefins having 8 to 12 carbon atoms include 1-octene (carbon number: 8), 1-nonene (carbon number: 9), 1-decene (carbon number: 10), 1-undecene (carbon number: 11), 1- and dodecene (carbon number: 12). It is preferable that the α-olefin as a raw material has 8 to 12 carbon atoms because the resulting polyα-olefin has a high flash point and excellent fluidity in a low temperature range.

The upper and lower limits of the content rate of the non-polar base oil contained in the self-viscous fluid according to the present embodiment are controlled so that the non-polar index of the base oil is in the range of 10 to 45. The content of the nonpolar base oil can usually be appropriately set in the range of 3 to 20 mass%, preferably 4 to 15 mass%, and more preferably 4 to 10 mass%.

The non-polar base oil contained in the self-viscous fluid according to the present embodiment preferably has a kinematic viscosity at 40°C of 50.0 mm2/s or less, more preferably in the range of 10.0 to 50.0 mm2/s, and 10.0 to 40.0 mm2/s. It is most preferable that it is in the range of s. It is more preferable that the kinematic viscosity of the non-polar base oil at 40°C is 50.0 mm2/s or less because it becomes easier to disperse the magnetic particles.

In addition, kinematic viscosity is kinematic viscosity measured by the same method as that for ester base oil.

The non-polar base oil contained in the self-viscous fluid according to the present embodiment preferably has a flash point of 200°C or higher, and more preferably 250°C or higher.

If the flash point of the base oil is 200°C or higher, the classification of the base oil composition under the Fire Protection Act changes from 3rd petroleum class to 4th petroleum class, so it is more preferable because the handling amount (designated quantity) of hazardous substances can be increased. In addition, the flash point is a flash point measured by the same method as that for ester base oil.

The non-polar base oil contained in the self-viscous fluid according to the present embodiment preferably has a pour point of -10°C or lower, more preferably -20°C or lower, particularly preferably -30°C or lower, and most preferably -50°C or lower. do. A pour point of -10°C or lower is more preferable because low-temperature fluidity is excellent. In addition, the pour point is the pour point measured by the same method as that for ester base oil.

The self-viscous fluid of the present invention may further contain other base oils in addition to the ester base oil and the non-polar base oil, as long as the effect of the present invention is not impaired. Examples of base oils other than ester base oils and non-polar base oils include higher fatty acids, higher alcohols, polyhydric alcohols, and ether base oils.

2-3. Alkylbenzene having an alkyl group having 10 to 24 carbon atoms, alkylnaphthalene having an alkyl group having 10 to 24 carbon atoms

The self-viscous fluid according to the present embodiment preferably contains alkylbenzene having an alkyl group having 10 to 24 carbon atoms, and/or alkylnaphthalene having an alkyl group having 10 to 24 carbon atoms. Alkylbenzene and alkylnaphthalene may be used individually or in combination. Alkylbenzene and alkylnaphthalene each function as a lubrication aid that improves the lubricity of self-viscous fluid. Additionally, alkylbenzene, alkylnaphthalene, and ester base oil all have polarity and are easily compatible with each other.

Alkylbenzene having an alkyl group having 10 to 24 carbon atoms is an aromatic hydrocarbon in which an alkyl group having 10 to 24 carbon atoms is bonded to one benzene ring. The alkyl group may be linear or branched. Additionally, one alkyl group may be bonded to the benzene ring, or multiple alkyl groups may be bonded to the benzene ring. Examples of alkylbenzene include monoalkylbenzene, dialkylbenzene, trialkylbenzene, and tetraalkylbenzene. The alkyl group contained in the alkylbenzene preferably has 10 to 20 carbon atoms, more preferably 12 to 18 carbon atoms, and even more preferably 13 to 18 carbon atoms.

The alkylbenzene is preferably one in which 1 to 4 alkyl groups are bonded to the benzene ring. Moreover, as alkylbenzene, it is preferable that the total carbon number of the alkyl group bonded to the benzene ring is 10 to 40, more preferably, the total carbon number of the alkyl group is 10 to 30, and even more preferably, the total carbon number of the alkyl group is 10 to 20. do.

Examples of the alkyl group include decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, henicosyl group, docosyl group, tricosyl group, tetracosyl group, etc. can be mentioned.

Alkylbenzene having an alkyl group having 10 to 24 carbon atoms may be used individually or in combination of two or more types.

Specific examples of the alkylbenzene having an alkyl group having 10 to 24 carbon atoms used in the magnetic viscous fluid according to the present embodiment are not particularly limited as long as it functions as a lubricating aid as described above, but examples include decyl benzene and undecyl benzene. , dodecyl benzene, tridecyl benzene, tetradecyl benzene, hexadecyl benzene, heptadecyl benzene, octadecyl benzene, nonadecyl benzene, icosyl benzene, henicosyl benzene, docosyl benzene, tricosyl benzene, tetracosyl benzene, etc. can be mentioned.

Alkylnaphthalene having an alkyl group having 10 to 24 carbon atoms is an aromatic hydrocarbon in which an alkyl group is bonded to one naphthalene ring. Examples of the alkyl group include those similar to the alkyl group bonded to the alkylbenzene described above. One alkyl group having 10 to 24 carbon atoms may be bonded to the naphthalene ring, or multiple alkyl groups may be bonded to the naphthalene ring.

The alkyl group in alkylnaphthalene preferably has 10 to 24 carbon atoms, more preferably 12 to 18 carbon atoms, and even more preferably 13 to 18 carbon atoms. The alkylnaphthalene is preferably one in which 1 to 4 alkyl groups having 10 to 24 carbon atoms are bonded to the naphthalene ring.

Alkylnaphthalene having an alkyl group having 10 to 24 carbon atoms may be used individually or in combination of two or more types.

Specific examples of the alkylnaphthalene used in the self-viscous fluid according to the present embodiment are not particularly limited as long as it functions as a lubrication aid as described above, but examples include decylnaphthalene, undecylnaphthalene, dodecylnaphthalene, tridecylnaphthalene, Examples include tetradecylnaphthalene, heptadecylnaphthalene, hexadecylnaphthalene, octadecylnaphthalene, nonadecylnaphthalene, icosylnaphthalene, henicosylnaphthalene, docosylnaphthalene, tricosylnaphthalene, and tetracosylnaphthalene.

If it contains only alkylbenzene having an alkyl group having 10 to 24 carbon atoms or alkylnaphthalene having an alkyl group having 10 to 24 carbon atoms, the lower limit of the content, or if both alkylbenzene and alkylnaphthalene are included, their The total content is preferably 5% by mass or more, more preferably 5 to 25% by mass, and even more preferably 10 to 25% by mass, relative to the total amount of base oil of the self-viscous fluid according to the present embodiment. It is preferable, and it is most preferable that it is in the range of 10 to 20 mass%. By setting the content to 5% by mass or more, the lubricity of the self-viscous fluid can be further improved, and the polarity of the self-viscous fluid can be further improved. By setting the content to 25% by mass or less, the content of the ester base oil can be suppressed from being relatively excessively reduced, and the effect of suppressing sedimentation of magnetic particles can be suppressed from being reduced.

The base oil contained in the self-viscous fluid according to the present embodiment preferably has a kinematic viscosity at 40°C of 50.0 mm2/s or less, and more preferably in the range of 10.0 to 40.0 mm2/s. It is more preferable that the kinematic viscosity of the base oil at 40°C is 50.0 mm2/s or less because it becomes easier to disperse the magnetic particles.

In addition, kinematic viscosity is kinematic viscosity measured by the same method as that for ester base oil.

The base oil contained in the self-viscous fluid according to the present embodiment preferably has a flash point of 200°C or higher, and more preferably 250°C or higher.

If the flash point of the base oil is 200°C or higher, the classification of the base oil composition under the Fire Protection Act changes from 3rd petroleum class to 4th petroleum class, so it is more preferable because the handling amount (designated quantity) of hazardous substances can be increased. In addition, the flash point is a flash point measured by the same method as that for ester base oil.

The base oil contained in the self-viscous fluid according to the present embodiment includes an ester base oil, a non-polar base oil, and specific alkylbenzene and alkylnaphthalene added as desired. The flash point in this case refers to the flash point calculated from the Flash-Point Blending Index (FPI for short). Hereinafter, when simply referring to “flash point”, this is meant.

The flash point mixing index for calculating the flash point is obtained from the flash point mixing index table described in Hydrocarbon Processing & Petroleum Refiner, June 1963, Vol. 42, No. 6. For example, when oil A with a flash point of 190°F (87.8°C) and oil B with a flash point of 330°F (165.6°C) are mixed at a volume ratio of 30:70, the flash point of the mixture is calculated as follows. Based on the flash point mixing index table described in the above document, the FPI of oil A is 30 and the FPI of oil B is 1.0. When the FPI of the mixture is calculated based on the FPI of each oil, "mixture FPI = (30/100) x (30) + (70/100) x (1.0) = 9.7." If this FPI 9.7 is applied to the flash point mixing index, the flash point equivalent to FPI 9.7 can be estimated to be about 230°F (110°C).

The base oil contained in the self-viscous fluid according to the present embodiment preferably has a pour point of -10°C or lower, more preferably -20°C or lower, particularly preferably -30°C or lower, and most preferably -50°C or lower. . A pour point of -10°C or lower is more preferable because low-temperature fluidity is excellent. In addition, the pour point is the pour point measured by the same method as that for ester base oil.

The content of base oil in the self-viscous fluid according to the present embodiment is preferably 10% by mass or more, more preferably in the range of 10 to 70% by mass, and 20 to 20% by mass. It is more preferable that it is in the range of 70 mass %, and it is most preferable that it is in the range of 20 to 60 mass %. By setting the base oil content to 10% by mass or more, magnetic particles can be dispersed and fluidity can also be improved. It is more preferable to set the base oil content to 70% by mass or less because the magnetic properties during excitation can be improved.

3. Inorganic cation exchanger with siloxane bond, silicone oil

The self-viscous fluid according to the present embodiment preferably further contains an inorganic cation exchanger having a siloxane bond and silicone oil. According to this configuration, the drag force when exciting the magnetic viscous fluid is further improved.

More specifically, the magnetic particles are dispersed in the base oil. Since the magnetic particles have cationic properties, they adsorb an inorganic cation exchanger having a siloxane bond. Additionally, silicone oil has a low surface energy and is dispersed without being dissolved in an ester base oil with a large solubility parameter. In addition, the inorganic cation exchanger having a siloxane bond and silicone oil have high affinity because both have Si, and the silicone oil exists in a state surrounding the magnetic particles to which the inorganic cation exchanger having a siloxane bond is adsorbed. I am guessing that they are doing it.

In this state, when a magnetic field is applied, the magnetic particles surrounded by silicone oil quickly combine and form clusters. By the presence of silicone oil around the magnetic particles, excessive aggregation of the magnetic particles is suppressed. For this reason, when measuring drag (viscosity) by applying a magnetic field, shear force occurs, but the cluster does not collapse, so it is assumed that the drag force is stable.

<Inorganic cation exchanger with siloxane bond>

Examples of inorganic cation exchangers having a siloxane bond include zeolite, silica, layered silicate, etc. Among these, considering wear resistance, zeolite is preferable. The inorganic cation exchanger having a siloxane bond may be used individually or in combination of two or more types. Both natural and synthetic products can be used.

Zeolite is composed of a skeleton of an anionic crystalline porous aluminosilicate and a cationic metal element M adsorbed on this skeleton. More specifically, tetrahedral SiO ₄ and AlO ₄ are used as basic structural units, and these are connected in three dimensions to form a crystal with pores (pores), and crystal water or cationic metal element M is adsorbed into these pores. It was a structured structure. The crystal structure of the zeolite is not particularly limited, and specifically, A-type zeolite, Examples include denite, clinoptilolite, and fallingite.

Layered silicate is a silicate compound that has a crystal structure in which the surfaces formed by ionic bonds or the like are stacked in layers with a weak bonding force. Layered silicates often have negative charges throughout the layers, and large positive ions enter between the layers to neutralize the negative charges. Since the layer charge is small, this cation can be exchanged with the cation in the solution and has cation exchangeability. Layered silicates, for example, smectites (bentonite, montmorillonite, beidellite, nontronite, saponite, hectorite, stevensite), vermiculite, kaolinite (kaolinite, halloysite, chrysotile, amesite), Mica family (muscovite, biotite, iron mica, phlogopite, white mica, paragonite, siderophyllite, istonite, polylithionite, trilithionite, lepidolite, zynwaldite, margarite, light, glaucoma), talc, palygorskite, sepiolite, magadiite, kanemite, kenyanite, synthetic fluorine mica, etc. Among these, smectite, vermiculite, and synthetic fluorine mica are preferred from the viewpoint of size of ion exchange capacity.

The cation exchange capacity of the inorganic cation exchanger having a siloxane bond is preferably 30 meq/100g or more, more preferably 30 to 400 meq/100g, even more preferably 60 to 350 meq/100g, and 60 It is more preferably in the range of 300 meq/100g, and most preferably in the range of 60 to 150meq/100g.

The cation exchange capacity of the inorganic cation exchanger with a siloxane bond is 260 meq/100g for mordenite, 120meq/100g for synthetic fluorine mica, 60 to 150meq/100g for smectite, 80 to 150meq/100g for montmorillonite, and 100meq/100g for vermiculite. to 150meq/100g.

The content of the inorganic cation exchanger having a siloxane bond is preferably 0.8% by mass or more, more preferably 0.8 to 4.0% by mass, and 1.0 to 3.5% by mass, based on the total amount of the self-viscous fluid according to the present embodiment. It is more preferable that it is a range, and it is most preferable that it is a range of 1.3 to 3.0 mass%. It is more preferable to set the content to 0.8% by mass or more because agglomeration of magnetic particles can be suppressed in a state where a magnetic field is not applied. It is more preferable to set the content to 4.0 mass% or less because clusters of magnetic particles can be appropriately formed when a magnetic field is applied.

<Silicone oil>

Silicone oil can be used without particular restrictions as long as it is incompatible with the ester base oil. Silicone oil is broadly divided into straight silicone oil and modified silicone oil. Examples of straight silicone oil include dimethyl silicone oil, methylphenyl silicone oil, and methylhydrogen silicone oil. Modified silicone oil includes reactive silicone oil and non-reactive silicone oil. Examples of the reactive silicone oil include various silicone oils such as amino-modified type, epoxy-modified type, carboxy-modified type, carbinol-modified type, methacryl-modified type, mercapto-modified type, and phenol-modified type. Non-reactive silicone oils include polyether-modified types, methylstyryl-modified types, alkyl-modified types, higher fatty acid ester-modified types, hydrophilic specially modified types, higher fatty acid-containing types, and fluorine-modified types. Among these, dimethyl silicone oil and fluorine-modified type silicone oil are preferable because they have low surface energy, and dimethyl silicone oil is more preferable considering ease of availability.

The lower limit of the silicone oil content is preferably 0.5% by mass or more, more preferably 0.5 to 3.0% by mass, and most preferably 1.0 to 2.5% by mass, based on the total amount of the self-viscous fluid according to the present embodiment. It is more preferable to set the content to 0.5% by mass or more because the inorganic cation exchanger having a siloxane bond can surround the attached magnetic particles. It is more preferable to set the content to 3.0% by mass or less because it can prevent a decrease in the dispersibility of the magnetic particles.

The mixing ratio of the inorganic cation exchanger having a siloxane bond and the silicone oil is preferably in the range of 2:8 to 8:2 in mass ratio, and more preferably in the range of 3:7 to 7:3.

A range of 2:8 to 8:2 is more preferable because it can improve the stability over time of the drag force during excitation.

The absolute value of the difference in solubility parameters between the ester base oil and the silicone oil is preferably 1.3 (cal/cm3) ^1/2 or more, more preferably 1.5 (cal/cm3) ^1/2 or more, and 1.8 (cal/cm3). It is particularly preferable that it is ^1/2 or more. It is more preferable that the absolute value of the difference in solubility parameters between the ester base oil and the silicone oil is 1.3 (cal/cm3) ^1/2 or more because the incompatibility between the ester base oil and the silicone oil can be improved.

<Other ingredients>

In the self-viscous fluid according to the present embodiment, in addition to each of the above-mentioned components, various other components may be used in combination depending on the purpose, as long as the effect of the present invention is not impaired.

Other ingredients include, for example, anti-wear agents, dispersants, surfactants, viscosity modifiers, fluidity improvers, sedimentation inhibitors, pour point lowering agents, extreme pressure agents, rust inhibitors, antioxidants, corrosion inhibitors, metal deactivators, anti-foaming agents, etc.

Examples of anti-wear agents include sulfur-based compounds such as sulfides, sulfoxides, sulfones, and thiophosphinates, halogen-based compounds such as chlorinated hydrocarbons, molybdenum dithiophosphate (MoDTP), and molybdenum dithiocarbamate (MoDTC). ), and organometallic compounds such as tricresyl phosphate.

One type of wear-resistant agent may be used individually, or two or more types may be used together.

The dispersant is added to improve the dispersibility of the magnetic particles in the base oil, and includes known low-molecular-weight dispersants and high-molecular-weight dispersants. Dispersants may be used individually, or two or more types may be used in combination.

Viscosity modifiers include, for example, castor oil, hydrogenated castor oil, fatty acid amides, beeswax, carnauba wax, benzylidene sorbitol, metallic soap, polyethylene oxide, sulfate ester-based anion activator, polyolefin, (meth)acrylic acid ester, Examples include polyisobutylene, ethylene-propylene copolymer, and polyalkyl styrene.

A viscosity modifier may be used individually by 1 type, or 2 or more types may be used together.

Examples of the fluidity improver include modified silicone oil. For example, straight silicone oil can be modified with alkyl, aralkyl, polyether, higher fatty acid ester, amino, epoxy, carboxyl, alcohol, etc. In addition, the modified silicone oil may be compatible with ester base oil. The fluidity improver may be used individually as one type, or may be used in combination of two or more types.

<Viscosity of self-viscous fluid>

The viscosity of the self-viscous fluid according to the present embodiment before excitation is preferably in the range of 0.02 to 1.0 Pa·s, and more preferably in the range of 0.03 to 0.6 Pa·s at 40°C. In addition, the measurement conditions for viscosity before excitation are as follows.

3 ml of magnetic viscous fluid is injected into the test plate of a rheometer DHR-2 manufactured by TA Instruments equipped with a magnetic measurement option, and the viscosity (Pa·s) is measured at 20 revolutions with a gap of 100 μm in an atmosphere of 40°C.

<Magnetic properties of magnetic viscous fluid>

As described above, the magnetic viscous fluid according to the present embodiment has the characteristic of having a large drag force when excited. The large drag force at the time of excitation means that in the magnetic viscous fluid of the present invention, when the content of magnetic particles in the total amount of the self-viscous fluid is 64 to 67% by mass, the maximum value of the viscosity at the time of excitation under the following conditions is 230. It refers to something that is greater than or equal to Pa·s. Moreover, the maximum value of viscosity at the time of excitation is preferably 230 Pa·s or more, and more preferably 240 Pa·s or more.

In addition, as described above, by further including an inorganic cation exchanger having a siloxane bond and silicone oil, excellent stability over time of drag force during excitation (viscosity stability over time) is obtained. Excellent stability over time (viscosity over time) of drag during excitation means that the stabilization rate B, described later, is 80% or more. Additionally, the stabilization rate A is preferably 70% or more, more preferably 80% or more, and especially preferably 90% or more.

The viscosity at the time of excitation was measured using the same measuring device as the device that measured the viscosity before excitation, under the same temperature atmosphere, applying a magnetic field of 0.8T DC 5 seconds after the start of the measurement, and measuring the magnetic field 215 seconds after the start of the measurement. This refers to the viscosity for 210 seconds after the application was stopped and the magnetic field was applied.

The stabilization rate A (%) is calculated based on the following equation.

Stabilization rate A (%) = (stabilization time A / total applied time) × 100

In addition, the stabilization time A represents the application time corresponding to 95 to 100% of the maximum value of the viscosity at the time of excitation.

The stabilization rate B (%) is calculated based on the following equation.

Stabilization rate B (%) = (stabilization time B / total applied time) × 100

In addition, stabilization time B refers to the application time corresponding to 90 to 100% of the maximum value of viscosity at the time of excitation.

(Method for producing self-viscous fluid)

The method for producing the magnetic viscous fluid according to this embodiment is not particularly limited. For example, magnetic particles, ester base oil, non-polar base oil, and, if necessary, alkylnaphthalene, an inorganic cation exchanger with a siloxane bond, silicone oil, and other components added as desired are added in a predetermined amount to a homogenizer. , a method of mixing using a processor with high shear force such as a bead mill or mechanical mixer. At this time, the ester base oil and the nonpolar base oil are mixed so that the nonpolar index consisting of the ester base oil and the nonpolar base oil is within a predetermined range. Additionally, in the production of self-viscous fluid, heating or cooling may be performed as needed.

(Mechanical device using self-viscous fluid)

The magnetic viscous fluid according to the present embodiment can be applied to various mechanical devices such as brakes, clutches, vibration isolators, and dampers of vibration dampers for controlling frictional force acting between objects. According to this configuration, in various mechanical devices, the magnetic viscous fluid has good drag force upon excitation, and deterioration of the rubber in contact with the magnetic viscous fluid can be well suppressed.

Example

Examples of the present invention are shown below, but these examples are provided to better understand the present invention and its advantages, and are not intended to limit the invention.

<Examples 1 to 14, Comparative Examples 1 to 3>

Each component shown in Tables 1 to 3 was placed in a beaker based on the mass ratios described therein, and stirred at 40 Hz for 5 minutes at room temperature using a universal vibration stirrer AD-MIX manufactured by Seiko Advance, to prepare a magnetic viscous fluid. . The raw materials for each component shown in Tables 1 to 3 are shown below.

(A) Magnetic particles

(a1) Carbonyl iron (average particle diameter D50=6.0㎛)

(B) Ester base oil

<Hindered ester>

(b1) Trimethylolpropane trioctanoic acid ester (SP value: 9.1 (cal/cm3) ^1/2 , kinematic viscosity at 40°C 16.0 mm2/s, flash point 260°C, pour point -57°C)

<Dibasic acid ester>

(b2) Sebacsandi(2-ethylhexyl) (SP value: 8.9 (cal/cm3) ^1/2 , kinematic viscosity at 40°C 11.3 mm2/s, flash point 228°C, pour point -66°C)

(b3) Adipic acid di(2-ethylhexyl) (SP value: 8.9 (cal/cm3) ^1/2 , kinematic viscosity at 40°C 7.8 mm2/s, flash point 205°C, pour point -68°C)

(b4) Diisodecyl adipate (SP value: 8.9 (cal/cm3) ^1/2 , kinematic viscosity at 40°C 14.2 mm2/s, flash point 232°C, pour point -63°C)

(C) Non-polar base oil

(c1) polyα-olefin (trimer of 1-decene, kinematic viscosity at 40°C: 17.2㎟/s, flash point 222°C, pour point -68°C)

(D) Alkylnaphthalene

(d1) Monoalkylnaphthalene having an alkyl group having 16 to 18 carbon atoms (kinematic viscosity at 40°C: 37.0 mm2/s, flash point 221°C, pour point -25°C or less)

(E) Inorganic cation exchanger with siloxane bond

(e1) Zeolite (crystal structure: mordenite series, cation exchange capacity: 160 to 190 meq/100g)

(F) Silicone oil

(f1) Dimethyl silicone oil (SP value: 7.2 (cal/cm3) ^1/2 , kinematic viscosity at 40°C: 37.8 mm2/s)

<Evaluation of rubber resistance properties>

For the magnetic viscous fluids of Examples 1 to 14 and Comparative Examples 1 to 3, solutions excluding magnetic particles were prepared as solutions for evaluating rubber resistance properties. 300 ml of each solution was added to each 500 cc beaker. Additionally, separately, NBR manufactured by AS-ONE was cut into a rectangle with width x length x thickness = 10 mm x 60 mm x 5 mm.

Next, each solution for evaluating rubber resistance properties was placed in a convection oven (DRF633TA manufactured by Advantest) heated to 100°C and left for 24 hours. Then, the above-described rectangular NBR was placed in the above-described beaker and used as a test sample. did.

After placing the test sample in the convection oven, take out the beaker 480 hours later, take out the NBR immersed in the magnetic viscous fluid, and wipe the oil on the surface of the NBR using Kimwipe (registered trademark) S200 manufactured by Nippon Seishi Cresia. has been removed. Then, the hardness (hardness after heating) of the NBR was measured by the method described later. Additionally, the hardness (initial hardness) of the rectangular NBR before being placed in the beaker was measured in the same manner.

· Measurement of hardness: Durometer: Measured using DUROMETER ADM-E manufactured by Niigata Seiki Co., Ltd. in accordance with JIS K 6253.

Three samples were prepared for each of the test samples for Examples 1 to 14 and Comparative Examples 1 to 3, and the above-mentioned rubber resistance properties were evaluated for all under the same conditions, and the hardness of NBR in the three samples was measured. The average was calculated. The calculation results are shown in Tables 1 and 2.

Next, the hardness change rate was calculated in the manner described later. The calculation results are shown in Tables 1 and 2.

· Hardness change rate = {(hardness after heating - initial hardness)/initial hardness} × 100 (%)

In addition, “-” in the hardness change rate shown in Tables 1 and 2 indicates expansion and contraction, and “+” indicates swelling.

<Evaluation of viscosity before excitation and viscosity during excitation>

3 ml of the magnetic viscosity fluids of Examples 1 to 7 and Comparative Examples 1 to 2 were injected into the test plate of a rheometer DHR-2 manufactured by TA Instruments equipped with a magnetic measurement option, and the viscosity was measured at 20 rotations with a gap of 100 μm in an atmosphere of 40°C. (Pa·s) was measured to measure the viscosity before excitation. The viscosity at the time of excitation was also measured using the same measuring device in an atmosphere of 40°C based on the following measurement conditions.

Magnetic field excitation conditions: A magnetic field of 0.8T DC was applied 5 seconds after the start of measurement, and application of the magnetic field was stopped 215 seconds after the start of measurement.

As described above, three samples of the self-viscous fluids for Examples 1 to 7 and Comparative Examples 1 to 2 were prepared, and the viscosity before excitation and viscosity during excitation were evaluated under the same conditions. The average of the measurement results of the viscosity before excitation and the viscosity during excitation of the NBR in the three samples was calculated. The calculation results are shown in Table 3.

Stability over time was evaluated by the stabilization rate A (%) and stabilization rate B (%) calculated based on the following formula. The calculation results are shown in Table 3.

Stabilization rate A (%) = (stabilization time A / total applied time) × 100

In addition, the stabilization time A represents the application time corresponding to 95 to 100% of the maximum value of the viscosity at the time of excitation.

Stabilization rate B (%) = (stabilization time B / total applied time) × 100

In addition, the stabilization time B refers to the application time corresponding to 90 to 100% of the maximum value of the viscosity at the time of excitation.

Examples 1 to 14 were all self-viscous fluids containing magnetic particles and a base oil. The base oil contained an ester base oil and a non-polar base oil, and the non-polar index of the base oil was in the range of 10 to 45. For this reason, it can be seen that in Examples 1 to 7, the maximum value of the viscosity during excitation is 230 Pa·s or more, showing good drag during excitation. In addition, in Examples 1 to 14, the absolute value of the hardness change rate relative to NBR was all less than 5%, and it had good rubber resistance properties.

Additionally, in Examples 1 to 7, the stabilization rate B was 80% or more, and the drag force during excitation had good stability over time.

On the other hand, in Comparative Examples 1 to 3, since the self-viscous fluid did not contain a non-polar base oil, the hardness change rate was 9% or more compared to NBR, and the rubber resistance properties were poor.

Figure 1 shows a graph showing the relationship between the nonpolar index in Tables 1 and 2 and the hardness change rate of NBR in Examples 1 to 4, 7 to 14, and Comparative Examples 1 to 3. From the graph in FIG. 1, it can be seen that when the non-polar index of the base oil is in the range of 10 to 45, the hardness change rate is 5% or less and has good rubber resistance properties.

Claims (5)

It is a magnetic viscous fluid containing magnetic particles and base oil,
The base oil includes an ester base oil and a non-polar base oil,
A self-viscous fluid, wherein the base oil has a non-polar index in the range of 10 to 45. According to paragraph 1,
A self-viscous fluid, wherein the ester base oil is at least one selected from hindered esters and dibasic acid esters. According to paragraph 1,
A self-viscous fluid further comprising alkylbenzene having an alkyl group having 10 to 24 carbon atoms, and/or alkylnaphthalene having an alkyl group having 10 to 24 carbon atoms. According to paragraph 1,
A self-viscous fluid further comprising an inorganic cation exchanger having a siloxane bond and a silicone oil. A mechanical device using the self-viscous fluid according to any one of claims 1 to 4.

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